In a mixer, beat butter with vanilla sugar until fluffy, about 3-4 minutes. Add eggs.,In a separate bowl, mix flour with baking soda and salt. Gradually add to the butter mixture. Divide dough in half.,To one half of the dough, add in vanilla extract. Lay the dough on a large sheet of parchment paper. Lay a second sheet of parchment on top of the dough. Roll dough to form a 12-inch x 8-inch rectangle. Freeze dough for about 15 minutes.,______,Remove both sheets of dough from freezer. Remove the top layer of parchment paper for each rectangle. Lay sheets of dough together (with parchment on the outside). Remove 1 sheet of parchment paper (dough should have 1 remaining on bottom). Slowly peel dough from the bottom parchment by rolling up the long end. You are going to form a log of dough. Tightly roll this dough and rewrap in parchment. Freeze until ready to use.,When ready to bake, wet fingertips with water. Roll log of dough in sprinkles. Slice 1/4-inch thick and bake on a parchment-lined baking sheet for about 7-9 minutes (in a 350°F oven).,Note: See my recipes for vanilla sugar. If you don't have vanilla sugar, scrape 1 vanilla bean into your granulated sugar and continue the recipe as written.